Let's start by understanding what decision trees are because they are the fundamental units of a random forest classifier. At a high level, decision trees can be viewed as a machine learning construct used to perform either classification or regression on some data in a hierarchical structure. In this article, I will only discuss the use of decision trees for classification. Decision trees use machine learning to identify key differentiating factors between the different classes of our data. By doing so, decision trees can take some input data and predict a class by running the data through a set of differentiating questions that it forms using machine learning.